A percutaneous, transvenous, endocardial approach has become standard practice for catheter ablation of several types of arrhythmias and pacemaker lead implantation. However, this approach has limitations, including the inability to access intramural or epicardial portions of arrhythmia circuits or inability to gain access to desirable tributaries of the coronary venous system. Technological improvements such as cooled-tip or larger-tip ablation catheters and different energy sources for tissue ablation have not completely solved the problem.
Before the advent of percutaneous catheter-based endocardial ablation methods, surgical epicardial approaches were used for treatment of refractory arrhythmias, particularly ventricular tachycardia (VT) and supraventricular tachycardia (SVT), by using an accessory pathway. Epicardial ablation has been achieved through various methods, including open-chest surgery, thoracoscopy, and by way of epicardial vessels such as the coronary sinus. However, despite the development of catheter-based, endocardial ablation techniques, some arrhythmia substrates might not be accessible from the endocardium. For example, VT from ischemic cardiomyopathy might have significant portions of the arrhythmia circuit in the epicardium. More recently, the percutaneous approach for epicardial mapping and ablation of VT has been shown to be feasible, primarily in patients with ischemic cardiomyopathy.
Currently, epicardial pacing is often required in small children, in patients with residual right-to-left shunts, and in patients with chambers that cannot be accessed by the transvenous route. Although endocardial pacing requires less extensive surgery than does epicardial lead implantation, there is concern about vascular obstruction, AV valve integrity, and the limitations of lead accommodation during growth with epicardial pacing. The risks have generally been outweighed by the higher acute and chronic stimulation thresholds of conventional epicardial leads, resulting in premature battery depletion and the need for subsequent operations. Recent advances in epicardial leads and surgical approaches have demonstrated improved early pacing and sensing thresholds. Prior studies evaluating epicardial leads in children have had low patient numbers or have involved series that predated both the introduction of lithium iodide batteries and steroid-eluting leads.
Therefore, a steerable sheath delivery system for percutaneous epicarcial access and a permanent lead for pacing and/or defibrillating epicardially is provided by the present invention.